Can you make, and sell, a car that goes one hundred miles on a gallon of gas? That's a question we should expect to hear soon from the X-Prize Foundation (the people responsible for the civilian space race.)

They are expected to announce a $25 million prize for creating a car that can go 100 MPG and, here's the kicker, selling a to-be-determined number of units.

One of the most promising recent developments that stands a real chance of competing for this prize is the concept of a Hydraulic Hybrid. We've heard of "hybrid" cars before and many people have fears regarding the safety and expense of batteries, but these hybrids don't use batteries.

Battery hybrids have electric motors that run off batteries that are charged by braking, a supplemental internal combustion (IC) engine (i.e., gas engine), and sometimes an overnight charge (i.e, a "pluggable" hybrid.)

Hydraulic Hybrids have a hydraulic motor (basically a system of pumps that use pressurized fluid for power). An IC engine powers the pumps to maintain vehicle speed, but most of the power used in acceleration comes for stored hydraulic energy captured during breaking.

A groundbreaking study released last week sounds a cautionary note to the consumer. Plug-ins do burn less gasoline than regular hybrids - and gobs less than gasoline-only vehicles - but the high cost of their bigger battery packs will probably neutralize even significant savings at the pump, according to a report by the American Council for an Energy-Efficient America (ACEEE)

I have looked into the costs vs savings argument myself, and there is compelling arguments to be made for staying with a gas-powered car if your only concern is money. However, there is more at stake than money. Hybrids, and especially PHEVs, reduce our dependence on foreign oil and are beneficial to the environment in terms of the reduction of CO2 emissions. Costs will come down as adoption rates climb.

"Who Killed The Electric Car?" asks Chris Paine in his recently released documentary of the same name. The documentary ultimately lays the blame at the feet of several people/organizations. This commentary from CNN provides a nice recap of the film and the issues it raises. For the most part, the motives of the parties involved are clear. The most difficult to understand, however, is the automakers themselves. The movie makes the case for their motives but never really spells them out. Here's the reasoning that I inferred from the evidence presented/hinted at:

mandate - the companies were annoyed at being told they must sell these cars.

profit - they never saw enough demand to allow them to go into mass production.

maintenance - the cars required so little maintenance that the manufacturers and dealers saw no hope of making money from the service/parts side of the business.